The major objective of the proposed research is to explain the pathogenesis of salmonellosis. Factors determining Salmonella virulence are relatively unknown; some strains cause a self-limited form of food poisoning, while others progress to a fulminating systemic infection. Information is unavailable to explain the local events in the small intestine affecting colonization, invasion, and fluid secretion. Preliminary research has revealed two potential virulence factors produced by Salmonella. The first factor can be described as a cholera toxin-like toxin that activates adenylate cyclase. Some experiments will emphasize determining the importance of this toxin in elevating cyclic AMP levels in epithelial tissue of rabbit intestinal loops infected with Salmonella. The relationship of this toxin to other intestinal virulence mechanisms (e.g., tissue invasion, mouse lethality, and fluid accumulation) will be investigated and environmental factors influencing the release of toxin from Salmonella cells will be studied. Sufficient knowledge of cultural parameters and toxin production has been generated to permit effective progress toward purifying the Salmonella toxin. Rapid in vitro methods (e.g., CHO floating cells assay and ELISA) will measure the toxin during fractionation. Since our recent bacteriophage investigations have confirmed that the toxin gene is not carried by a temperate phage, we will attempt to determine if the toxin gene is located on a plasmid or on the bacterial chromosome. Following purification, the chemical structure and antigenic composition of the Salmonella toxin will be compared to that of cholera toxin. The second potential Salmonella virulence factor (a cytotoxin) is described here for the first time. This cytotoxin causes damage to cultured cell monolayers and inhibits incorporation of 3H-leucine into protein. Attempts will be made to determine if similar toxicity occurs in the intestinal mucosa of Salmonella infected, intestinal loops. Following purification and elucidation of its chemical structure, the relationship between this cytotoxin and the Salmonella toxin will be examined, and frequency of cytotoxin production by Salmonella strains will be assessed. Finally, the cytotoxin will be tested in an in vitro system to demonstrate direct inhibition of protein synthesis. The proposed research involving these two potential virulence factors should improve our understanding of the pathogenic mechanisms of Salmonella infections.